Do you read? If so, a bookcase would be nice. You do need something big enough that it looks planned.

However, could the couch be moved closer to the window to leave just enough room for a table with a plant and lamp on it?

A sofa table with two lamps seems like a natural fit. You can run an extension cord along the baseboard and under the couch to the outlet.

A couple of ottomans or garden stools tucked under can serve as extra seating, or you could choose a table with a shelf and place your blanket basket there.

It's difficult to give suggestions without seeing the whole room tbh.... do you have a dining area, kitchen table near this room?

What is the room used for? TV, family time etc?

Does the rest of the room have enough room for accent pieces ?

Is it 'spare space' ?